<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #box {
      width: 500px;
      height: 500px;
      border: 1px solid #ccc;
    }
    .img_all {
      width: 100px;
      height: 100px;
      float: left;
    }
  </style>
</head>
<body>
  <div id="box">
    <div class="img1 img_all">1</div>
    <div class="img2 img_all">2</div>
    <div class="img3 img_all">3</div>
    <div class="img3 img_all">4</div>
    <div class="img3 img_all">5</div>
    <div class="img3 img_all">6</div>
  </div>
</body>
</html>